Image sensor and manufacturing method thereof

Abstract

An image sensor includes a storage device, where the storage device includes a memory element, a first dielectric layer and a light shielding element. The memory element includes a storage node and a storage transistor gate, where the storage transistor gate is located over the storage node. The first dielectric layer is located over a portion of the storage transistor gate. The light shielding element is located on the first dielectric layer and includes a semiconductor layer. The semiconductor layer is electrically isolated from the memory element, where the light shielding element is overlapped with at least a part of a perimeter of the storage transistor gate in a vertical projection on a plane along a stacking direction of the memory element and the light shielding element, and the stacking direction is normal to the plane.

What is claimed is: 
     
       1. An image sensor, comprising:
 a storage device, comprising:
 a memory element, comprising:
 a storage node; and 
 a storage transistor gate, disposed over the storage node; and 
 
 a light shielding element, disposed over the memory element and comprising:
 a semiconductor layer, electrically isolated from the memory element, wherein a projection of the light shielding element covers a projection of the storage transistor gate on a plane along a stacking direction of the memory element and the light shielding element. 
 
 
 
     
     
       2. The image sensor of  claim 1 , wherein the storage node comprises a P-N junction. 
     
     
       3. The image sensor of  claim 1 , wherein the memory element further comprises:
 a first dielectric layer, disposed between the memory element and the light shielding element; and 
 a first metal silicide layer, disposed over and electrically coupled to the storage transistor gate through a recess comprised in the first dielectric layer and accessibly revealing the storage transistor gate, 
 wherein the storage transistor gate comprises:
 a gate electrode, revealed by the recess comprised in the first dielectric layer; and 
 a gate dielectric layer, disposed between the storage node and the gate electrode, 
 wherein the first metal silicide layer is in contact with the gate electrode exposed by the recess comprised in the first dielectric layer. 
 
 
     
     
       4. The image sensor of  claim 1 , wherein the light shielding element further comprises:
 a second metal silicide layer, disposed over and wrapping around the semiconductor layer. 
 
     
     
       5. The image sensor of  claim 1 , wherein the storage device further comprises a substrate, wherein the storage node is disposed in the substrate, and a projection of the storage node is within the projection of the storage transistor gate on the plane along the stacking direction, and
 wherein the first dielectric layer comprises:
 a first dielectric portion, extending over the storage transistor gate; and 
 a second dielectric portion, extending over the substrate and offset from the storage transistor gate, and the first dielectric portion and the second dielectric portion are connected to one another, and 
 
 wherein the light shielding element comprises:
 a first shielding portion, extending over the first dielectric portion. 
 
 
     
     
       6. The image sensor of  claim 5 , wherein the light shielding element further comprises:
 a second shielding portion, extending over the second dielectric portion, and the first shielding portion and the second shielding portion are connected to one another. 
 
     
     
       7. The image sensor of  claim 5 , wherein a thickness of the light shielding element is non-constant. 
     
     
       8. The image sensor of  claim 5 , wherein the storage device further comprises
 a second dielectric layer, disposed between the light shielding element and the memory element, wherein the first shielding portion stands on the second dielectric layer and extending over the first dielectric portion. 
 
     
     
       9. The image sensor of  claim 8 , wherein the light shielding element further comprises:
 a second shielding portion, standing on the second dielectric layer and extending over the second dielectric portion, and the first shielding portion and the second shielding portion are connected to one another, 
 wherein a surface of the first shielding portion is coplanar with a surface of the second shielding portion. 
 
     
     
       10. An image sensor, comprising:
 a photosensitive device; 
 a storage device, adjacent to the photosensitive device, comprising:
 a substrate; 
 a P-N junction, embedded in the substrate; 
 a gate electrode, covering the P-N junction; and 
 a shielding structure, disposed over the substrate and electrically isolated from the gate electrode, wherein the shielding structure comprise:
 a first shielding layer, comprising a first portion disposed over the substrate with a recess penetrating therethrough, wherein a projection of the first portion is overlapped with a projection of the gate electrode on a plane along a stacking direction of the substrate and the gate electrode, wherein the first shielding layer is made of a semiconductor layer; and 
 a second shielding layer, covering the first shielding layer; 
 
 
 a driving circuit, adjacent to the storage device; and 
 an interconnect, disposed over and electrically coupled to the photosensitive device, the storage device, and the driving circuit. 
 
     
     
       11. The image sensor of  claim 10 , wherein the first shielding layer further comprises:
 a second portion, disposed over the substrate, wherein a projection of the second portion is offset from the projection of the gate electrode on the plane along the stacking direction, 
 wherein the projection of the first portion is between the projection of the second portion and the projection of the gate electrode on the plane along the stacking direction. 
 
     
     
       12. The image sensor of  claim 11 , wherein a first surface of the first portion and a second surface of the second portion are coplanar to each other, and the first surface and the second surface are facing away from the gate electrode. 
     
     
       13. The image sensor of  claim 11 , wherein a first surface of the first portion and a second surface of the second portion are curved surfaces, and the first surface and the second surface are facing away from the gate electrode. 
     
     
       14. The image sensor of  claim 10 , wherein the second shielding layer is made of a metallic silicide material. 
     
     
       15. The image sensor of  claim 10 , wherein a projection of the recess formed in the first portion is less than the projection of the gate electrode on the plane along the stacking direction.